Mazer's (What I Believe ) engaging if somewhat familiar novel centers on a 10-year-old girl's mixed feelings for her older sister. Sprig and Dakota used to play and giggle together, “but when Dakota turned twelve in August? Boom, just like that, something fell out of the sky and hit her on the head, she also turned bossy and know-it-all.” Sprig's resentment intensifies when their father, an architect/engineer, leaves on a lengthy business trip that later extends (without so much as a quick flight home) to a month or two in Afghanistan. Dakota chides Sprig for crying when she misses their father, and when Sprig worries out loud about the dangers of Kabul, Dakota tells her she's being stupid. And why does Dakota get to talk to Dad first each time he calls home? Mazer weaves in subplots that are slightly too neat—Sprig visits an elderly neighbor (whose attention the sisters compete for) at just the right moment to save her from a stroke; a fight, also well-timed, with her best friend teaches Sprig the perils of jealousy—and she wraps up the conflicts rather tidily. But the author excels at depicting the complexity of preteens' emotions and relationships, especially sibling relationships; many readers will recognize their own feelings here. Ages 9-12. (Sept .)